A protein kinase can phosphorylate an enzyme and activate it by

Signal transduction

Explanation:

A signal molecule binds to a receptor.

A conformational change in the signal-receptor complex activates an enzyme.

Second messenger molecules are released.

Protein kinases are activated.

Target proteins are phosphorylated.can be defined as the process in which a physical or chemical signal is transmitted through a cell as a series of molecular events inform of protein phosphorylation are catalyzed by protein kinase and this ultimately result into a cellular response. However, the protein that is responsible for the detection of stimuli is commonly refers to as receptors or sensor.

protein synthesis is an example of feedback mechanism which in homeostasis